Vehicle engines may need to be intermittently serviced by a mechanic for diagnostic purposes. Diagnostics may involve visually inspecting engine components (for example, to identify scoring damage, camshaft alignment issues, etc.), rotating an engine to a selected position to identify component damage (for example, to detect hydro-lock) and/or spinning an engine (for example, to perform vacuum tests).
The inventors herein have recognized that some of the diagnostics can be time, cost, and complexity-intensive. In addition, for diagnostics that are sensitive to the position of the engine, small fluctuations in the engine position can substantially corrupt the result of the diagnostics. Further, it may be difficult to hold the engine in a selected position due to compression forces in the engine.
In view of the above issues, the inventors have developed a method for a hybrid vehicle system that allows accurate engine positioning for diagnostic purposes. In one example, the engine may be diagnosed by a method comprising, during selected non-combusting engine conditions in which the vehicle has been placed into a service mode, rotating the engine via an electric motor responsive to an operator input. In this way, engine positioning can be improved enabling a mechanic to reliably complete vehicle diagnostics.
In one example, a hybrid vehicle may be placed in a service mode during conditions when the engine is not combusting and the vehicle is not being driven. A mechanic may use a service diagnostic tool that is coupled to the vehicle to request the service mode. As such, in this mode, the mechanic may be able to perform one or more diagnostic tests, some of which may require specific engine positioning. For example, certain diagnostic tests may require the piston of a specific cylinder to be at a specified position. The mechanic may select a diagnostic test to be performed and may request a specific engine position. In response to the request, an electric motor of the vehicle system, coupled to the engine via the driveline, may be operated. The engine may be rotated by the electric motor to the requested engine position. Further, motor torque may be used to hold the engine at the requested position until mechanic has completed the diagnostic test. Upon completion, the mechanic may request a new position so as to perform another diagnostic test, in which case the electric motor is operated to rotate and reposition the engine. Else, if no further tests or engine positioning requests are received, the vehicle may be shifted out of the service mode, and returned to the operational mode where the vehicle can be driven.
In this way, an electric motor of a hybrid vehicle system can be used during a service mode to assist in engine positioning for diagnostics. By operating the motor to rotate and hold the engine at a specified position, accuracy of engine positioning is improved, and reliability of position-sensitive diagnostics is increased. By using existing vehicle hardware to position the engine, the need for costly and complex diagnostic tools is reduced. Overall, vehicle diagnostics can be simplified, and made time and cost efficient.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.